Dr. Marla Shapiro: Can your cat make you sick? Preventing toxoplasma

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When we counsel pregnant women, we often talk about smoking alcohol and medication use and the importance of knowing what you can and cannot do during pregnancy. But what about your pets? Are there any concerns there?

There sure is! Cats are hosts of a common parasite called toxoplasma. These parasites multiply in the cat's intestine. Millions of something called oocytes are shed in a cat's feces during its first infection.

These oocytes become infectious when they are eaten and develop further. This parasite is spread in blood and infects all tissues, mainly the central nervous system, eyes, muscles, and most importantly in pregnant women in the placenta.

The cysts can remain in infected mammals and humans for life in the skeletal muscles and brain. Later on there can be reactivation of disease in immunocompromised people infected with the cysts.

According to MotherRisk at the Hopsital for Sick Children, as many as 25% of Canadians are IgG-positive for Toxoplasma due to past exposure. Immunoglobulin M (IgM) titres indicate current infection.

Although only a minority of people -- between one and two in every 10 -- has symptoms, advisers say extra measures to control the disease may be needed.

The disease is spread by direct contact with cats or eating contaminated food. We can be infected through undercooked or raw meat (lamb, pork) infected with cysts or through food or water contaminated with oocytes excreted by cats (eg, unwashed vegetables). Transmission of Toxoplasma has also been reported through contaminated drinking water.

While the infection usually has no symptoms or very mild symptoms (fever, malaise, enlarged lymph nodes and en enlarged spllen or liver); in immunocompromised patients, the infection can be very serious.

Women who contract Toxoplasma infections BEFORE pregnancy usually do not transmit it to their fetuses. But if a mother becomes infected during pregnancy, toxoplasmosis can be transmitted across the placenta. This ratio would translate into 40 to 400 cases annually in Canada

Clinical manifestations of toxoplasmosis in fetuses and neonates vary. One can see impacts on the brain with hydrocephalus as well as inflammation of the retina. A baby that presents with an enlarged spleen and liver, microcephaly, convulsions, fever, and small-for-gestational-age newborns all suggest Toxoplasma. Most neonates have no symptoms at birth on routine pediatric examination. Deafness, mental retardation, and learning difficulties are often detected only later in life.

Risk of congenital toxoplasmosis is somewhat lower if infection occurs during the first trimester (10% to 25%) than if it occurs during the third trimester (60% to 90%). But the severity of congenital infection is substantially higher if infection occurs during the first trimester.

So what do you need to know to prevent an infection. According to the CDC here are some suggestions:

Food should be cooked to safe temperatures

Fruits and vegetables should be peeled or thoroughly washed before eating.